williams performance company manufactures sports cars. after making a sale, the salesperson sends the car to be detailed before the customer takes it home. detailing the car takes 30 minutes at a cost of $17 per hour for direct labor and $5 per car for materials. if the average salesperson sells three cars per day, what is the average cost per 5-day week for detailing cars? (do not round intermediate calculations. round your final answer to 2 decimal places.)